Will Extremes Become the Norm under Future Climate Change? · 1. Dynamically downscale global...
Transcript of Will Extremes Become the Norm under Future Climate Change? · 1. Dynamically downscale global...
Will Extremes Become the Norm under
Future Climate Change?
October 25, 2016
Renalda El-Samra, Elie Bou-Zeid, Hamza Kunhu Bangalath,
Georgiy Stenchikov and Mutasem El-Fadel
Introduction Study Results
Climate change is an imminent threat to water and agriculture sectors
worldwide
In-depth assessments of local impacts are a must to guide adaptation
strategies
This is especially needed in the eastern Mediterranean basin
(complex topography,
water scarcity, poverty,
increase in population,
increase in temperature,
decrease in precipitation)
http://www.worldatlas.com/
Introduction Study Results
Over complex topographic region, we expect an uneven distribution of
extreme events (heat waves, droughts, flooding)
Corresponding future climate cannot be evaluated by Global Climate
Models (GCMs) only, due to their coarse resolution
High resolution regional climate models (RCMs) are now used to
dynamically downscale results from GCMs, to produce information at a
local scale necessary to assess climate change impacts
Mahoney et al., 2011
Introduction Study Results
Objectives
1. Dynamically downscale global climate predictions over the eastern
Mediterranean basin to a regional scale (focus: Lebanon) using the
Weather Research and Forecasting (WRF) model forced by the High
Resolution Atmospheric Model (HiRAM) for the past and the future
2. Use these simulations to evaluate the impact of climate change on
temperature and precipitation extremes
Lebaupin Brossier et al., 2009
Introduction Study Results
Study Area: Lebanon
Eastern Mediterranean basin
Area = 10,452 km2
High complex topography
(results applicable in similar locations)
High climate variability:
Subtropical coast
Mediterranean at low altitudes
Cold weather at high altitudes (snow)
Semi-desert inland plain
Introduction Study Results
GCM: HiRAM (resolution 25km)
RCM: WRF, 2 domains (9:3km)
One-way nesting (no nudging)
MODIS (2001) land use data
Dynamics and physics:
Dudhia SW radiation
RRTM LW radiation
Eta PBL scheme
Noah LSM
WSM 6-class microphysics scheme
Vertical levels: 28
HiRAM IC/BC/SST every 6hrs
Introduction Study Results
Select the two extreme years for the past (a mild/wet year, and a
hot/dry year) and eight years in the future (one hot/dry year per RCP
per decade) based on the following anomaly score: � � � �� = �� − ��� �� − �� + − � − �max � − �
Pi is the cumulative precipitation for year i
Pi
is the decadal-average of yearly precipitation Pi
Ti is the yearly median temperature for year i
Ti
the decadal-average of median temperatures Ti
The resulting minimum negative score will correspond to the
critical/worst year of the decade from a water resources perspective
Introduction Study Results
RCP4.5:
2020,
2029,
2040,
2050
RCP8.5:
2017,
2023,
2035,
2050
Precipitation
Tmedian
2011 2015
Introduction Study Results
Rainfall
RCP4.5
+3%
-29% -35%
-20%
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Snowfall
RCP4.5
+18%
-52%
+42%
+49%
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Hydrological Impacts
Increase in consecutive dry days (CDD) (up to
75% in mountains)
Decrease in consecutive wet days (CWD) (> 50%
in inland regions)
Decrease in days of heavy rainfall (R10MM) and
very heavy rainfall (R20MM) (up to 50% in
inland zones)
Decrease in maximum one day precipitation (all
regions except on the mountains,
where WRF projected a slight increase)
COAST
MOUNTAINS
INLAND
SOUTH
INLAND
CENTRAL
INLAND
NORTH
Introduction Study Results
Impacts on Average Temperature
Tavg during RCP4.5:
• Decreases in the winter (1.3⁰C) & spring (1.4⁰C)
• Increases in summer (1.5⁰C) & autumn (2.5⁰C)
Tavg during RCP8.5:
• Decreases in the winter (0.63⁰C) & spring (0.94⁰C)
• Increases in summer (1.2⁰C) & autumn (2.2⁰C)
Most affected regions are the mountains
and inland regions
(increase in summer ~ 3⁰C & autumn ~ 3.9⁰C )
COAST
MOUNTAINS
INLAND
SOUTH
INLAND
CENTRAL
INLAND
NORTH
Introduction Study Results
Extreme Heat Impacts
Tmax are expected to increase on average from 1% (coast) to 15%
(inland)
Inland region experiencing the worst warming on average
CI +5.9⁰C
NI +6.9⁰C
CI +6.2⁰C
Introduction Study Results
Extreme Heat Impacts
Summer days (Tmax>25⁰C): increase 98% in RCP4.5 & 82% in RCP8.5
over the mountains
Consecutive summer days (CSU) (Tmax>25⁰C)
could double in the inland region, & triple
for the mountainous region in both RCPs
Percent of very warm days :
increases up to 25% (RCP4.5) and up to
21% (RCP8.5) in inland zones
COAST
MOUNTAINS
INLAND
SOUTH
INLAND
CENTRAL
INLAND
NORTH
Introduction Study Results
Impacts on Cold Spells
Tmin are projected to decrease across all regions and more
pronounced in RCP4.5 (1.7⁰C) than RCP8.5 (0.3⁰C)
Number of consecutive frost days (CFD) in RCP4.5 would increase by
over two folds in all regions
<0⁰C
NI -4.8⁰C
Introduction Study Results
This research focused on extreme future weather over the complex
region of the Eastern Mediterranean: we found that these extremes
will be significantly exacerbated by climate change.
All WRF future simulations projected a warming over the study region
with different intensities depending on the year and/or RCP under
consideration, with the worst case scenario occurring in the inland and
the mountainous regions
A significantly drier climate over nearly the entire study area is
predicted by the middle of this century, with reduction in annual
precipitation of about 30%
Precipitation (and snowmelt) in mountains feeds the most productive
agricultural regions and these changes could undermine future
production due to future water shortage
Acknowledgments
USAID-NSF PEER initiative (Grant Number –AID-OAA-
A_I1_00012), US National Science Foundation (Grant #
CBET-1058027), NCAR (Project P36861020) and KAUST
Supercomputing Laboratory
Thank you
Questions?